Means for reducing the dwell in hydraulic presses



April .11, 1944. P. E. FLOWERS MEANS E03 REDUCING THE DWELL IN HYDRAULICPRESSES Filed Sept.- 27. 1940 Pam. E.

Patented Apr. 11, 1944 UNITED STATES PATENT OFFICE MEANS FOR REDUCINGTHE DWELL IN HYDRAULIC PRESSES Paul E. Flowers, Mount Gilead, Ohio,assignor to The Hydraulic DevelopmentCor-poration, Inc.,

Wilmington, Del., a'corporation of Delaware Application September 27,1940, Serial No.358,'l04 v Q 14 Claims. (CI. 6052) v This inventionrelates to presses, and in particular to hydraulic presses with fastadvancing movement of the press platen during the first portion of theworking stroke.

In presses of the said character a dwell occurs during the shift fromrapid advance to pressing speed, which dwell is caused by the fact thatit takes the pump some time to build up pressure in a large cylinder andto compress the oil therein as well as to take care of slight cavitationdue to the cylinder not being entirely filled at the time the shifttakes place. Thesaid dwell increases naturally with the size of thepress, and in modern large presses appreciably in creases the timerequired for a working cycle.

Accordingly, it is an object of the inventionto provide a method of anddevice for reducing the time of the dwell that occurs in a large pressduring the shift from rapid advance to pressing speed.

It is another object of the invention to provide a hydraulic press witha rapid advance movement of the press platen during the first portion ofthe working stroke, in which additional fluid pressure is exerted uponthe press platen at the time when the shift from rapid advance topress-' ing speed is effected. 7

It is a further object of the invention to provide a press of the typereferred to above, in

which, in response to the engagement of the work piece by the dieconnected with the press invention will appear more clearly from theyfollowing specification in connection with the accompanying drawing, inwhich:

Figure 1 diagrammatically illustrates a press provided with the dwellreducing means according to the present invention.

Figure 2 shows the dwell reducing means of Figure 1 on a somewhat largerscale. said means being shown during the loading of the accumulator.

Figure 3 is a section similar to Figure 2, show-- ing the accumulatorwhile being unloaded.

General arrangement In order to reduce the time of the dwell that occursduring the shift of the-rapidadvance to pressing speed, the pressaccording to the present invention is provided with an accumulator whichis charged with fluid during the rapid advance stroke of the pressplaten and unloads its fluid into the upper portion ofthe press cylinderas soon as the die supported by the press platen engages a. work piece.To this end the accumulator is provided with valve means which iscontrolled by a combined surge unloading valve so that when-thesurgevalve closes at Structural arrangement Referring now to the drawingin detail, I designates the press cylinder having a cylinder bore 2 inwhich a double-acting piston 3 is reciprocably mounted. The piston 3 hasconnected therewith a ram 4 carrying the press platen 5. To preventleakage from the press cylinder bore 2, a making 6 is provided at thelower portion of the press cylinder I and compressed against a pressring I by means of a gland 8. Communicating with the lower portion ofthe press cylinder 2 is a conduit 9 comprising a safety valve l0 andleading to a main cylinder relief and pump bypass valve' l I. The maincylinder relief and pump by-pass valve- I! does not form a part'of thepresent invention and for a. more detailed description thereof referencemay be had to U. S. patent the press platen. Also communicating with thevalve H is a conduit [2 connected to a safety valve l3 and leading tothe upper portion of the cylinder bore 2. The conduit l2 alsocommunicates with the valve H by a branch pipe l4.

Branching oil from the conduit 9 is a conduit build up the f I 5 leadingto a surge valve II which, as far as its upper portion is concerned,operates in the same manner and is similarly constructed as the s surgevalve disclosed in U. 8. Patent No. 2,193,248

to Walter Ernst. The purpose of the said portion 5 of the surge valve IIconsists in preillling the uppuportion of the press cylinder during therapid advance of the press platen. To this end the surge valve ll opensthe bores l 'l due to the sucthe press cylinder I may flow through thebores [1 into the upper portion of the cylinder bore 2.

In addition to the features of the surge valve disclosed in U. 8. Patent2,193,248, the surge valve shown in the drawinghas the further p rp seof controlling the now of additional pressure fluid into the upperportion of the cylinder 2. According to the invention, the shaft I! ofthe surge 29 valve. is provided with a'valve member generally designated20, which comprises two spaced pistons 2| and 22 interconnected by aninterconnecting member 23 of smaller diameter than the pistons 2| and22. The pistons 2| and 22 are reciprocably mounted in the surge valvecylinder 24 which communicates through a conduit 25 with one side of areversible variable delivery pump 28, the other side of whichcommunicates with a conduit 21 leading to the conduit 9. The

variable delivery pump 28 is provided with a. flow control member (notshown) in a manner well known to those skilled in the art, which, whenshifted into one extreme position, causes the" pump to deliver in onedirection, whereas, when shifted into another position causes the pumpto deliver in the opposite direction. The flow control member isfurthermore adapted to occupy an intermediate or neutral position inwhich the pump delivers substantially no fluid. The

now control member is actuated in one direction by means of a spring 28normally urging a bell crank lever' 29 in anti-clockwise direction,

said bell crank lever being pivotally connected with a rod an which, inits turn, is connected with the flow control member, and being shiftableabout the pivot 2|. Operatively connected with the rod ll is a solenoid22 which, when energized,

causes movement of the rod II and thereby of the flow control membertoward the right against the thrust of the springs 2|.

Branching of! from the conduit 25 is a conduit 33 leading into the fluidtank It and comprising a check valve 24.

The surge valve cylinder 24 comprises a spring 35 the lower end of whichengages the bottom of the surge valve cylinder 24 whereas the upper endengages the surge valve piston 22. The spring 35 is arranged so as tocontinuously urge the pistons 2| and 22 upwardly. Provided in the bottomof w eiiect communication between the interior of the as cylinder andthe upper portion of the press cylinder bore 2. The surge valve cylinder24 has connected therewith two conduits 35 and 31, each comprising acheck valve, 38 and 39 respectively. However, while the check valve 28opens in the to direction away from the surge valve cylinder 24, thecheck valve 25 opens in a direction toward the surge valve cylinder 24.The conduit 35 leads to a recess 42 in an unloading valve generallydesignated 4|. The unloading valve 4| comprises 75 on a working stroke,the pump 26 is started in a casing 42 with a spring chamber 43 housing aspring 44 which constantly urges the plunger 45 downwardly. The plunger45 has interconnected piston portions 46 and 41,.the latter of whichcarries a control plunger 48 adapted when in raised position to effectcommunication between the conduit 35 and the conduit 49 leading into aconduit 50, one end of which communicates with the upper portion of thecylinder bore 2, whereas the other end leads to a tonnage control valve5|. The tonnage control valve 5| is responsive to a predeterminedpressure in the press cylinder and adapted, at the attainment of thispressure, to break the circuit comprising the solenoid 32 so that thelatter is deenergized. The tonnage control valve 5| does not form a partof the present,

invention and for a more detailed description thereof reference may behad to'U; S. patent application, Serial No. 214,772 to Walter Ernst,filed June 20, 1938, which has matured into Patent No. 2,224,957.

The plunger portion 46 is adapted to enter a recess 52 comprising abreather opening 53. The plunger portion 41 is adapted to be lifted by apredetermined pressure in the conduit 36a leading from the recess 40 tothe accumulator 54 which pressure is conveyed from the conduit 3611.through the passageway 55 into the recess 56 in the valve casing 42.The'check valve 39 is adapted to communicate with the recess 51 in theunloading valve 58 which in its construction fully corresponds to theconstruction of the unloading valve 4!. Thus the unloading valve 58comprises a spring chamber 59 with a spring 50, plunger portions GI, 62,63 and recesses 64 and 65. The recess 65 communicates through apassageway 66 with the conduit 61 leading to the accumulator 54.However, the unloading valve 58 is so set that the plunger portion 62interconnected with the plunger portions GI and 53 is lifted at a lowerpressure than the plunger portion 41 of the unloading valve 4|. Theaccumulator 54 is, in its loaded position, filled with fluid up to thelevel indicated at 68 whereas the lowermost level which the fluid in theaccumulator may reach is indicated by the reference numeral 69. Theunloading valve 58 is set so that it closes when the level 89 isreached. If desired, a floating valve may be arranged in the accumulator54 which automatically closes the conduit 61 at the attainment of apredetermined lowermost level. The fluid, preierably oil, in theaccumulator 54 is under the pressure of a gas, such as .an inert gas,for instance nitrogen. The accumulator 54 is provided with a fillingline Ill controlled by a shutofi valve "H which, when in open position,allows filling of the accumulator with the desired gas.

The press platen 5 is provided with a platen arm 12 adapted to engage acollar-13 adjustably mpimted on a control rod 14 which carries twoviously stated, isurged by spring 28 into anticlockwise direction. Thecollar 16 is adapted to engage the flange 11 on the press cylinder l forlimiting the downward stroke of the control rod 14.

' Qperation Assume that all parts occupy the position shown in Figure 1and that the plunger portion 3 of the unloadin'g'valve 58 interruptscommnnication between the conduit and the conduit 61. If it is nowdesired to start the press any convenient manner. Thereupon the oper-'ator closes the circuit comprising the solenoid 32 sothat the latter isenergized moving the pump to full stroke forward position. As soon asthe pump begins to deliver fluid into the conduit 25 and, consequently,to withdraw fluid from the. lower portion of the-press cylinder bore 2through the conduits 9 and 21, the press ram .4 with the platen movesrapidly downwardly at the rate at which fluid is withdrawn from belowthe piston 3. The suction created by the downward movement of the piston3 is conveyed throughthe bore 18 in the surge valve cylinder 24 andkeepsthe pistons 2| and 22 in their lowermost position so thatcommunication between the conduit 25 and the conduit 36 prevails. Whilethe space above the piston 3 during the downward movement thereof isfilled with fluid passing from the tank I8 through the surge valve boresI1, fluid delivered by the pump 26 through the conduit 25 passes aroundthe interconnecting member 23 into-the conduit 36'from where it flowsthrough the check valve 38,the recess 40 and the conduit 36a into theaccumulator 54, thereby charging the latter. As soon as a predeterminedpressure is built up in the accumulator 54, this pressure through theconduit 61 and the passageway 66 in the unloading valve 58 upon theplunger portion 62 so that the latter together with the plunger portion63 is lifted against the thrust of the spring 60. Pressure fiuid fromthe accumulator 54 may then pass through the recess 51, the check valve38 into the conduit 31. However, since the piston 2I closes the conduit31, no fluid can escape from the said conduit. Before the die carried bythe press platen 5 engagesa work piece, the accumulator 54 is charged toa predetermined level so that the desired pressure is establishedtherein. When the said level, for instance the level 68, has beenreached,

-a predetermined pressure higher than the pres-' sure necessary foropening the valve .58 is established. If now the pump 26 delivers fluidinto the conduit 36 so that the pressure in the-accumulator exceeds saidlast mentioned high pressure, this pressure acts through conduit 36a,passageway 55 and recess 56 upon the piston portion 41 so as to lift theplunger 48 against the thrust of the spring 44 thereby enabling fluid topass from the conduit 36, through the recess 40 and the conduits 49 and50 directly into the upper portion of the press cylinder bore 2.

As soon as the die carried by the platen 5 engages the work piece, theram 4 stops temporarily so that,the suction created in the upper portionof the press cylinder 2 is eliminated, whereupon the spring 35 lifts thepistons 22 and 2| to their uppermost position thereby closing theconduit 36 while establishing communication between the conduit 31 andthe bore 19. As a result thereof, the pressure fluid accumulated in theaccumulator 54 discharges'through the conduit 61, the recess 51, checkvalve 39, conduit 31 and bore 19 into the upper portion of the presscylinder 2, thereby instantaneously filling any voids which may prevailabove the piston 3 and also compressing the fluid above the piston 3. Inthis way the dwell heretofore observed with presses of the type underconsideration is practically eliminated,

thereby reducing the time required for a working cycle. It will beappreciated that the check valve 80 prevents the pressure fluid incylinder 2 from is conveyed and 49, but allows pressure fluid to passfrom conduit 49 into conduit50.

'- "When the fluid in the accumulator 54, during the" unloadingoperation, falls below the level 68, the pressure in the accumulator islower than the pressure exerted by the spring 44 so that the lattermoves the plunger 48 downwardly thereby again interrupting,communication between the conduit 36a and the conduit 48. The lowerpressure unloading valve 58 remains open'until the fluid in theaccumulator 54 has fallen to the level 69. Figure 3 shows the positionof the unloading valve during the unloading operation at a, time whenthe fluid in the accumulator has reached a level intermediate the levels68 and 68. Whenthe press platen 5 has reached its lowermost position inwhich a predetermined pressure acts upon the piston 3, this pressureconveyed through the conduit 58 to the tonnage control valve 5|'actuates the latter which, in its turn,

of the press platen. Pressure fluid is then delivered by the pump 26through the conduits 21 and 9 into the lower portion of the presscylinder bore 2. The pressure in the conduit 9 is conveyed through theconduit I5 to the surge valve I6 where it acts upon a piston (not shown)which is connected with the shaft I8 so as to move the pistons 2| and 22downwardly into a position in I pelled by the piston 3 during theretraction stroke can escape through the bores I1 into the fluid tankI8. Since the conduit 25 is now the suction side with regard to thepump, the check valve 38 closes, thereby' preventing the fluid in theaccumulator 54 from falling below the level Atthe end of the upwardstroke of the ram 4,'the press platen 5 engages the collar 13 so as tolift the control rod 14 which in its turn, .by means of the collar 15,shifts the bell. crank lever '29 and the rod 30 pivotally connectedtherewith in such a manner as to move the pump 26 to neutral orno-delivery position. The ram 4 thencomes to a standstill and the pressis ready for a new cycle.

It willbe understood that I desire to comprehend within my inventionsuch modifications as come within the scope of the claims.

Having thus fully described my invention, what I claimas new and desireto secure by Letters Patent, is: 1. A hydraulic press comprising incombination a press ram, a first fluid source adapted to supply pressurefluid to said ram, a second fluid source adapted to supply additionalpressure fluid to said ram, means for conveying pressurefluid from saidfirst fluid source to said second fluid source to build up apredetermined pressure in the latter, means responsive totheestablishment of said predetermined pressure in said second fluidsource for establishing hydraulic connection between said first fluidsource and said ram, means operable at the engagement of the work pieceto be shaped by said ram or a die connected acting upon valve plunger48through conduits 50 thereto for conveying fluid pressure from saidsecond fluid source to said ram'to speed up the start of the actualpressing stroke, and means responsive to a predetermined discharge ofsaid second fluid source for again interrupting hydraulic 'connectionbetween said second fluid source and said ram, while said flrst fluidsource remains hydraulically connected with said ram.

2. In combination in a hydraulic press, a press mm, a fluid reservoir,means responsive to the initiation of a working. cycle of said ram foradmitting fluid from said reservoir to said ram, a main fluid sourceadapted to supply pressure fluid to said ram, an additional pressurefluid source adapted to supply pressure fluid to said ram independentlyof said main fluid source, means responsive to the start of theadvancing movement of said ram for causing said main fluid of said ramprior to its slowing down to pressing speed for the-actual pressingaction, fluid storage means independent of said tank and adapted to besupplied with pressure fluid by said fluid source, controlling meansadapted in responseto a predetermined pressure condition in'saidcylinder during said fast advancing movement to move into a flrstposition for establishing fluid connecsource to load said additionalfluid sourcemeans responsive to a predetermined pressure on said ramprior to the start of the actual pressing stroke thereof forinterrupting hydraulic con-' nection between said reservoir and said ramand for instantaneously supplying fluid from said additional fluidsource to said ram to supplement the fluid from said main fluid source,and means responsive to a predetermined discharge from said additionalfluid source to said ram to interrupt hydraulic connection between thelatter and said additional fluid source, while said main fluid sourcecontinues to supply pressure fluid to said rain to cause the latter toeffect its actual pressing stroke.

.3. A hydraulic press comprising in combina- ,tion a press cylinder, apress ram reciprocably mounted in said cylinder, 9. fluid source adaptedto supply pressure fluid to said ram during the advancing and retractionstroke thereof, an additional fluid source adapted to supply pressurefluid to said ram only during the advancing stroke thereof, a fluidreservoir, means responsive to a suction effect in said cylinder forestablishing hydraulic communication between said reservoir and saidcylinder, means for controlling said additional fluid source so as toefl'ect hydraulic communication between the latter and said ram prior tothe start of the actual pressing action of said ram and to interruptsaid hydraulic communication between said reservoir and said cylinder,and means for hydraulically disconnecting said additional fluid sourcefrom said cylinder while said ram continues its pressing stroke.

4.- A hydraulic press comprising in combination, a press cylinder, a ramreciprocable in said cylinder, a surge.tank, means responsive to asuction eflect in said cylinder for hydraulically connecting the samewith said tank, a fluid source adapted to supply pressure fluid to saidram for selectively causing an advancing and a retractder, means forinitiating a fast advancing movement of said ram, afluid source adaptedto supply pressure fluid to said cylinder for advancing said ram, afluid tank for supplying fluid to said cylinder during said fastadvancing movement tion between said fluid source and said storage meansto load the latter, and also adapted at the ,end of said fast advancingmovement to move into a second position for establishing fluidconnectionof said cylinder with both said fluid source and said storagemeans, while simultaneously interrupting fluid connection between saidtank and said cylinder, and means responsive to a predetermineddischarge of fluid from said storage means for interrupting fluidconnection between said storage means and said cylinder withoutpreventing the delivery of -fluid from said fluid source to saidcylinder.

6. A hydraulic press comprising in combination a press ram, means forinitiating an advancing movement of said ram, a fluid source adapted tosupply pressure fluidto said ram for advancing the same, fluid storagemeans for storing fluid under pressure, said fluid storage meansbeing,

fluid source to said ram.

'I. In combination in a hydraulic'press, apressram, pumping meansadapted to supply pressure fluid to said ram to actuate the same, meansfor storing fluid under pressure, means for hydraulically connecting thepressure side of said Dumping means with said fluid storing means duringthe pressing-stroke of said ram prior to the actual pressing actionthereof to load said storing means, means responsive to a firstpredetermined pressure in said storing means for by-passing thedischarge of said pumping means to said ram, means responsive to apredetermined pressure on said ram for unloading fluid from said storingmeans to said ram, and means responsive to a second predeterminedpressure in said storing means lower than said flrst predetermined pres,sure for interrupting hydraulic communication between said pumping meansand said fluid storing means while said pumping means delivers fluid tosaid ram to cause the latter to carry out its pressing action. V I

8. A hydraulic press comprising in combination a press ram, a fluidsourcejadapted to supply pressure fluid to said ram for actuatingthesame, a

of said accumulator, valve means for controlling hydraulic communicationbetween said storage tank and said ram, a controlling valve adapted inresponse to a predetermined pressure in said accumulator to eflecthydraulic communicationbetween the latterand said valve'meanspnd meansoperatively connected with said valve means for establishing hydrauliccommunication .between said accumulator and said gain in response to apredetermined pressure on the latter.

9. In combination in a hydraulic press, a press ram, pumping means i'orsupplying pressure fluid to said ram, fluid storage means for storingfluid under pressure, controlling means movable into a flrst positionfor unloading fluid from said fluid 1 storage means to said ram andmovable into a second position for establishing hydraulic connectionbetween said storage means and said pumping means to cause the latter-toload said storage means, means responsive to the moveposition forestablishing hydraulic connection between said pumping means and saidram, means responsive to the initiation of an advancing comprising incombina-.

.10, ment of said controlling means into said flrst' operable advancingand retracting means for reciprocating said ram, means for initiating anadvancing stroke of said ram, pumping means adapted to supply pressurefluid selectively to said advancing or retracting means, fluid storagemeans adapted to supply additional fluid to said advancing means, meansresponsive to the initiation of an advancing stroke of said ram forconveying pressure fluid from said pumping means to said storage meansto load thesame while preventing fluid connection between said advancingI,

means and said pumping means, means responsive to a predeterminedresistance encountered by said min during said advancing stroke forhydraulically connecting both said storage means and said pumping meanswith said advancing means, and means responsive to the unloading of apredetermined quantity of fluid from said storage means for againinterrupting fluid connection between said storage means and said ad-:vancing means without preventing fluid connec-' tion between saidadvancing means and said pumping means to allow said advancing stroke oisaid ram to continue. r

11. A hydraulic press comprising in combination a press ram, a fluidsource adapted to supply pressure fluid to said ram, fluid storage meansadapted to be loaded by said fluid source, means responsive to apredetermined pressfieinsaid fluid storage means for interrupting thesupply of pressure fluid from said fluid source to said storage meanswhile establishing fluid connection between said fluid source and saidram, and means adapted to unload fluid from saidfluid storage means tosaid ram in responseto resistance oflered by a work-piece to theadvancing movement of said ram. 7

12. A hydraulic press comprising incombination a press cylinder, a pressram reciprocably mounted in said cylinder, a tank containing-fluid. asurge valve adapted 'toeflect communication between said tank and saidpress cylinder to pre flll said cylinder, during the first portion ofthe working stroke oisaid ram, said surge valve being also adapted tointerrupt said communication in response to a predetermined pressure insaid cylinder, a fluid source for supplying pressure fluid to saidcylinder, fluid storage means independent oi said tank and adapted to besupplied with pressure fluid from said fluid source, controlling meansoperable by said surge valve for establishing hydraulic communicationbetween said fluid storage means and said press cylinder, and means forinterrupting the supply of pressure fluid from said fluid source to saidfluid storage means during the actual pressing action of said ram.

13. In combination in a hydraulic press, a press ram, a fluid pressurepump for supplying fluidpressure to said ram, an accumulator adapted tobe loaded by said pressure pump, a surge tank independent or saidaccumulator, means responsive to the initiation of a pressing cycle toestablish hydraulic connection between said surge tank and said ram andbetween said pump and said accumulator for filling the'latter, meansre-. sponsive to a predetermined loading of said accumulator forconveying the discharge of said pump to said ram, means responsive to apredetermined resistance encountered by said ram or a die connectedthereto for conveying fluid from said accumulator to said ram to shortenthe dwell thereof, means operable concomitantly with the establishmentof said last mentioned connection (or interrupting hydrauliccommunication between said tank and said ram, and means responsive to apredetermined discharge of said accumulator for interrupting hydraulicconnection between said accumulator and said ram while saidpumpcontinues to deliver fluid to said ram.

14. In combination in a hydraulic press, a press cylinder, a ramreciprocable in said cylinder, a fluid source adapted to supply pressurefluid to said cylinder for actuating said ram, fluid storage meansadapted to be loaded by said fluid source, a control member movable'fromone position into another position, or vice versa, means responsive tothe movement of said control member into one position for establishinghydraulic connection between said fluid source and said storage means tocause loading of the latter and also responsive to the movement of saidcontrol member into the other position for unloading fluid from saidstorage means into said cylinder in addition to fluid passingsimultaneously from said fluid source into said cylinder, and meansresponsive to a predetermineddecrease in pressure in said storage meansduring said unloading operation for interrupting hydraulic connectionbetween said storage means and said cylinder without impairing thesupply or fluid from said fluid source to said cylinder.

' PAUL E. FLOWERS.

